1. Field of the Invention
The present invention relates to portable terminal apparatuses and, more particularly, to a portable terminal apparatus equipped with an antenna.
2. Description of the Related Art
In recent years, a mobile communications technology is quickly developed and the portable terminal or personal digital assistant equipment as represented by a cellular phone has become popular rapidly. Since the portable terminal has become connectable with the Internet, a strong demand has been made by users to enlarge a liquid crystal display device incorporated in the portable terminal apparatus. For this reason, the personal digital assistant equipment of a fold-up or flip type has become widely used. The flip type portable terminal has a body part having operational keys such as ten keys and a lid part that is connected to the body part and provided with a liquid crystal display device.
The portable terminal apparatus is required to be provided with an antenna so as to perform radio communications in connecting with the Internet, etc. Conventionally, a whip antenna has been widely used for the portable terminal apparatus, which can be extended for use and retracted during a time of standby. However, the whip antenna must protrude from the portable terminal apparatus even when the antenna is accommodated in the portable terminal apparatus, which may be a problem in portability. Additionally, the whip antenna is larger in its size than other component parts constituting the portable terminal apparatus, which prevents the portable terminal from being miniaturized. Thus, a built-in type antenna, which is incorporated inside the portable terminal apparatus, has become used (refer to Japanese Laid-Open Patent Application No. 7-221822).
FIG. 1 and FIG. 2 show an antenna built-in type portable terminal apparatus 1 as conventional example. The portable terminal apparatus 1 shown in the figures is a fold-up or flip type cellular phone. FIG. 1 is a perspective view of the portable terminal apparatus 1 viewed from a bottom side. FIG. 2 is a cross-sectional view taken along a line A1-A1 of FIG. 1. It should be noted that an illustration of a lid part is omitted and a body part 2 is illustrated solely in each figure.
As shown in each figure, the body part 2 comprises a housing 4 and an antenna 5, a printed circuit board 6 and electronic parts 7 that are incorporated in the housing 4. The lid part (not shown in the figures) is rotatably attached to the body part 2 by a hinge part 3. Additionally, a speaker 8, electrodes for electric charge and a lid 14 for replacing a battery cell are provided on the bottom of the housing 4.
FIG. 3 is an enlarged view of the antenna 5 incorporated in the portable terminal apparatus 1. Conventionally, the antenna 5 built in the portable terminal apparatus 1 uses a multilayer flexible board, and an antenna wiring 11 formed on a base member 10. The antenna wiring 11, which serves as an antenna, constitutes a helical antenna by being patternized in a spiral shape. Each end of the antenna wiring 11 is extended to a connector part 12, and the connector part 12 is connected to the printed circuit board 6. It should be noted that an opening part 10a is formed in a central part of the base member 10 as shown in FIG. 3.
According to the above-mentioned structure, in which the antenna wiring 11 is formed on the single base member 10 and each end of the antenna wiring 11 is extended to the connector part 12, there is a part where the antenna 11 crosses itself as shown in FIG. 3. In FIG. 3, the antenna wiring 11 crosses at the part indicated by the reference numeral 13 (hereinafter, the part where the antenna wiring 11 crosses is referred to as an intersection part 13).
Naturally, the antenna wiring 11 must be insulated so that no short-circuiting occurs at the intersection part 13. For this reason, conventionally, a multilayer flexible board is used so as to form the intersecting parts of the antenna wiring 11 in different layers so as to prevent the antenna wiring from short-circuiting.
The antenna 5 having the above-mentioned structure is stuck on a bottom surface 4a of the housing 4 as shown in FIG. 2. The antenna 5 is stuck on the bottom surface 4a in a state where the plane of the antenna 5 matches the plane of the bottom surface 4a, that is, the antenna 5 and the bottom surface 4a are parallel to each other. Moreover, the arranged position of the antenna 5 is determined to be at a part where the density of the electronic parts is small on an individual type of the portable terminal apparatus basis. The arranged position of the antenna 5 is selected to be a side part of the speaker 8 in the example shown in FIG. 1.
However, in the above-mentioned conventional portable terminal apparatus 1, since the planer antenna 5, in which a spiral antenna wiring 11 is formed on the single base material 10, is used, there is a limitation arises in the location of the antenna 5 in the portable terminal apparatus 1. For this reason, it is difficult to locate the antenna 5 with a sufficient communication efficiency, which may affect the communication function of the portable terminal apparatus 1. Moreover, if it is attempted to provide a high communication efficiency to the conventional antenna 5, the antenna may become large, which requires a space to accommodate the enlarged antenna 5. Accordingly, there is a problem that the size of the portable terminal apparatus 1 increases.